Telephone.



P. L. JENSEN & E. S. PRIDHAM. TBLBPHUNB. APPLIOATIONYFILED MAB. 19, 1912. l 1,088,283 Patented Feb. 24, 1914,

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P. L. JENSEN & E. S. PRIDHAM.

TELEPHONE. APPLICATION FILED MAR. 19, 1912. .t 1,088,283. vPatented Feb. 24, 1914,

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UNITED V STATES PATENT OFFICE.

PETER L. JENSEN- AND EDWIN S. PRIDHAM, 0F NAPA, CALIFORNIA, ASSIGNORS T0 COMMERCIAL WIRELESS & DEVELOPMENT CO., 0F SAN FRANCISCO,l CALIFORNIA,

A CORPORATION 0F ARIZONA.

TELEPHONE.

To all 'whom it may concern:

Be it known that we, PETER L. JENSEN. a subject of the King of Denmark, and EDWIN S. PRIDHAM, a citizen ofthe United States, both residing at Napa, in the county of Napa and State of California, have invented new and useful Improvements in Telephones, of which the following is a specification.

This invention 4relates to the class of instruments employed in telephony for trans-y forming received currentA variations into sound vibrations.

The object of the present invention is to provide an instrument whereby, on account of its greater sensitiveness, speech or signals may be received with much greater clearness and desired loudness than with the instruments now in use; this being accomplished by an apparatus wherein a coil consisting of a number of turns of wire is so disposed in a magnetic field that it ac; tuates a diaphragm when current fiows through the coil.

It is a'well known fact that when a current flows through a Wire, magnetic lines of force surround the wire, the strength of l these lines of force being proportionalto the current fiowing through the wire. Looking at the end of the wire, if the current flows away from the observer, lines of force will be created in a plane at right angles tothe conductor in a clock-wise direction; if the current flows toward the observer, the direction of the lines of force will be created in a counter-clockwise direction. The lines of force around the conductor act Ias if rigidly connected to the conductor, any force acting on the lines of force thus acting on the material conductor. If a wire-carryling current is disposed ein a magnetic field so as to cut transversely the lines of force of the field, a force' acts upon .the conductor, due to the reaction of the magnetic lines of force, caused by the current fiowing in the' wire with the lines of force of the magnetic field. y

The present invention comprehends the employment of fan intense magnetic field .and a conductor, through which variable currents may iiow, disposed in this intense.

Specification of Letters Patent.

Application filed March 19, 1912.

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Patented Feb. a4, 1914. serial No. 684,718. A

ductor carrying current, when disposed in a i magnetic eld at right angles to the direction of the lines of force is the product of three factors; L, the length of the conductor; C, the current lowin in the conductor; andH, the strength of t e magnetic field.; the equation being f LXCXI-I-:F

measured in absolute units. It is obvious that any change in any one of the factors on the vleft hand side of the equationfwill produce a change in F. In this equation C represents the current flowing in the conductor. The current which represents the voice variations is comparatively weak, in telephone work, and when the distance over which thevcurrent must flow' becomes great the current becomes exceedingly wealn If 4the two factors L and PIy be made large, the resultant force F may be comparatively large, even,when C is very weak. If C is a varying factor, as it is in the telephonie transmission of speech, and the two factors In this air-gap there is disposed a rectangular coil consisting of many turns of wire. Within this coil there is placed an iron core. The coil is free from the core and is mounted` to allow an oscillatory movement about the core. The iron core is inserted in the air-gap to cut down the reluctance of the magnetic circuit. The disposal of the coil in the air-gap is such that the Wires of the two long sides of the rectangular coil cut transversely thelines of force in the densest part of the field. The shape of the coil and its position in the magnetic ,field is important, as the correct working and the` maximum sensitiveness is determined by it. In practice we have found that the best results have been obtained by using a rectangular coil .of many Iturns of 4fine wire erably wound upon a form of non-conducting material. rI his coil is disposed in a strong magnetic field so that its length may be cut transversely by a maximum number of lines of force. The coil is supported so as to be free to oscillat and is connected by a rigid arm to a diaphragm.A

fL and H are constant, then the force. will Ve have found by actual experiment that the coil disposed in the magnetic field will vibrate accuratelycorresponding withthe 'voice vibrations and. that the inertia of the` Figure 1 is a cross section. Fig. 2 is av front elevation of the device with diaphragm and connecting arm omitted. Fig. 3 is a modified form showingv in section. Fig. 4 is a modified form showing in section. Figs. 5, 6.and 7 are respectively side, front l and plane views of the apparatus as actually `Aconstructed and used. Figs. 8 and 9 show the construction and method of support of an improved form of mounting.

Having reference to Fig. 1, M M is an electromagnet of the horseshoe type, energized by the coils R R', having the pole pieces N-S. C is a rectangular coil, preferably. woundWit-h many turns of fine wire. The coil C is 'so disposed in the magnetic field between the pole ,pieces N-S that its length is cut at rightangles by the lines of force of the field. The coil C is mounted on bearings, as shown by the bearing P. These bearings may be pivots, springs or any support which will permit an oscillatory movement of the coil C. In practice we have made use of springs, which permit a torsional movement, with al high degree of success. Within the coil C is a fixed iron core F, 'around which the coil Cis free to oscillate. This core F is inserted in the magnetic field to cut-down the reluctance of the magnetic circuit. The coil C is connected by an arm or link A to the diaphragm D, -so that any movement of the coil C is transmitted accurately to the diaphragm. The electromagnet M M is energized by. a source of constant current, .as from primary or storagejcells or from a unipolar dynamo, it being necessary v.that the energizing current be smooth and constant. It is to be noted that the coil C, consisting of many turns of wire, is free to vibrate and is without inductive relation to any adjacent cirber, glass, etc.

1 l cuit. It is the only circuit disposed in the magnetic field and is connected directly into v the telephone` circuit by the leads t t. This' 55 coil C of 'many turns of wire is movable by the forces generated -in the field and this movement is transmitted directly to the diaphragm by the arm` A. The form on which the coil is -wound is preferably made of nonconducting material, such as-fiber, hard rub- FigyQ showsa detail of the apparatus. In this figure the disposal of the coil C is shown between the pole pieces N-S. The iron coreF is inserted within the coil C, but

is free from it. The coil C is here shown supported on pivots P P. The telephonie currents enter and leave the coil C through the terminals t t. A` permanent magnet -may be used to produce the magnetic field in which the coil C is disposed.V

In Fig. 3 a modified form of the instrument is shown. In.this form two instruments similar in construction to Fig. 1 are combined to act on a single diaphragm.

' Fig. t shows another modifiedform which shows one electro-magnet provided with a plurality .of air-gaps, in which coils are inserted acting on independent diaphragms.

Figs. 5, 6 and 7 are views of Fig. 1 from the side, the front and above.

The method of mounting our coil'for oscillation is important. We have found that in order to give the highest type of articulation there must be no freedom of the pivots, and also for the practical use of the instrument, the support of the coil should be such that no adjustment of the bearing should be necessary.

In the use of this instrument as a telephone receiving instrument, it is 'seen that the distance through which the coil turns is very slight, due to the abrupt changes in direction of current. The method of support made use of by us with especial success eliminates all lost motion and reduces the turning friction to a negligible factor. This is accomplished by the use of springs of peculiar construction which permit a slight torsional movement of the coil, but hold it rigidly in respect to any other movement. These springs are the sole support of the coil, taking the place of pivots and bearings. They are rigidl attached from the coil to the supporting ame. As the force needed to permit a slight torsional 'movement of the springs is very slight, a method of support is gained, whereby a solid connection may be had between the coil and the supporting frame, yet allowing a hi h efficiency of operation. By the use of tiis method of lsupport the detrimental effect of expansion and contraction due to temperature changes is eliminated. Thus, the use of this method of support is of great practical advantage in the use of this instrument for the receiving of telephonic speech. Referring to Fi 8, a method of support for the coil C is s own, which is very practical and substantial. Sa and Sb are the supports for the coil C. They are rigidly connected from the coil C to the supporting frame V V. Each of these supports is'fmade up of two thin fiat rectangular pieces of spring material combined in planes at right angles to each other, as shown in Fig. 9. This method of construction gives rigidity to the coil in a direction both parallel and perpendicular to the winding of the coil, while allowing an easy torsional movement.

centrated magnetic fields. so that all of the convolutions are practically cut by or intersect equally dense lines of magnetic force and will act equally and with maximum efficiency' to impart rotative effort.. to the coil whenever current is fiowing in the. coil, the rotative effort being in a direction dependent upon the direction of the current flow; i. c., a unidirection current will produce torque in one direction, and an alternating current, torque alternately in opposite directions. lith such an arrangement, it will be seen thatthe-movement will correspond accurately to the character, strength and duration of the current flowing in the coil, and there being no normal bias, the coil will move with equal freedom and power in either direction from its normal position. c y

The diaphragm D is connected through rigid connections with the coil, so as to be moved Vpositively thereby in both directions from normal position, and consequently the direction, amplitude and duration of the diaphragm movements correspond to the direction, strength and duration of the currentflowing in the coil.

There the sound creating parts, e., the diaphragm and actuating devices therefor have no normal bias and move to either side of normal position with equal amplitude and duration, the highest efiiciency is attained by utilizing the sound waves from both sides of the diaphragm, and in the instrument illustrated the diaphragm is located at an intermediate position in a sound box and the listening tubes are connected with the box on opposite sides of the diaphragm.

In an instrument such as that herein de.

scribed, particularly where used for long distance telephonic communication, the currents which actuate the coil are exceedingly lig-ht, and therefore the instrument must, as far as possible, eliminate any counteracting influence. As heretofore constructed,

'receiving instruments have almost invariably had the coils so arranged with respect to the core and surrounding parts, and the latter were of such construction that the coils acted in a measure as choke coils, thereby preventing the passage and consequent action of a very large proportion of the actuating current, but the present instrument is designed so as to avoid or prevent'. any

such retarding or counteracting inliuence, and in accomplishing this result the core F which is located within the coil C operates as would the secondary of a transformer or induction coil, by permitting of the generation and 'dow of secondary electric currents in a direction opposite to the direction of current flow in the coil itself. This function of the core F is -entirely independent of its function in Athe magnetic circuit, and it may be accomplished by ar- -ranging the core with an unbroken periphery in proximity to and parallel with the convolutions of the coil throughout the whole length of' -theconvolutions so as to provide an unbroken or 'closed circuit in which secondary currents may fiow with the minimum obstruction and resistance. To obtain this result, it is important that the core and pole piecesshould be solid or nonlaminated, inasmuch as a laminated construction such as is important in motor and transformer construction would defeat the very objects of the present inventionor reduce the,l efliciency to a point where the instrument would only becomparable to that of instruments in ordinary use.

Having thus described our invention, what we claim and desire to secure by Letters Patent is i l. A telephone embodying a magnet having an air gap forming a dense magnetic field, a diaphragm, an oscillatory coil forming part of the linecircuit connected with the diaphragm and located in the air gap, and a support for said coil formed of thin flat resilient parts arranged in intersecting planes parallel with the axis of oscillation of' the coil, whereby the coil is held rigidly against bodily movement, but is free to oscillate by torsional fiexure of the support.

2. A telephone embodying a magnet having an air gap forming a dense magnetic field, a diaphragm, an oscillatoryv coil forming part of the line circuit and located in PETER L. J ESSEN. EDWIN S. PRIDHAM.

lit-nesscs CHARLES EDELMAN, VALTER Rnmrnns. 

